Device and method for mobile handling of wood chips

ABSTRACT

The present invention relates to a method and a device for mobile handling of wood chips, comprising a mobile platform ( 2 ) on which a wood chipper ( 3 ) is provided, a chip conveyor ( 4 ) connected to the chipper, a packaging device ( 6 ) and a packaging casing ( 7 ) provided at the packaging device ( 6 ) provided in order to package chips ( 9 ) into a tubular package ( 8 ) by means of said packaging casing ( 7 ), whereby said chip conveyor ( 4 ) is in the form of a screw conveyor with a screw ( 41 ), the outfeed end of which is provided to feed chips to a compaction device ( 5 ) positioned in connection with said packaging device ( 6 ).

TECHNICAL FIELD

The present invention relates to a device for mobile handling of wood chips comprising a mobile platform on which a chipper is provided, a chip conveyor connected to the chipper, a packaging device, and a packaging casing arranged at the packaging device in order to package chips in a tubular package by means of the said packaging casing.

PRIOR ART AND BACKGROUND

In recent years, chips from forest waste have become an increasingly important raw material, but its supply is currently limited by several factors. Of the raw material available today only a small percentage is utilized, some 10 percent, as a result of transport problems, among other things. The method that is generally used today is primarily based on a harvester (the logging machine) compiling branches and tops, so-called forest residue, that is subsequently hauled away by a forest tractor to a processing yard. This method has many disadvantages, such as:

-   -   1 Hauling away is generally not done concurrently with logging.     -   2 Hauling on sleighs often carries along ground contaminations         and other contaminations.     -   3 The landing must often contain a minimum quantity.     -   4 Chipping is generally done only in the spring and summer.     -   5 The net root amount will be very modest for the land owner.

Due to these disadvantages, generally less than 10 percent of the available raw material from the final logging is used and often nothing from thinning. Some 80 million cubic meters are currently logged in Sweden, and since branches and tops form about 20 to 25% of a tree, it is likely possible to increase the yield from raw tree material by 15 to 20 million square meters, representing a gross income of around SEK 3 to 4 billion.

U.S. Pat. No. 4,044,525 discloses a method together with a device, and its subject matter is to provide a solution to the aforesaid problems. The device comprises a mobile unit with a chipper, which may be fed with the desired raw wood for direct production of wood chips immediately in connection with logging. A fan device is provided in connection with a wood chipper in order to feed the chips to an outfeed pipe. At the outfeed pipe, tubular packaging material is provided in order to wrap and package them in connection with the outfeed in the form of tubular wood chip packages. However, this prior-art method has not yet reached the market, probably due to a plurality of disadvantages, which in practice has meant that the problem could not be solved in an exact way. Due to the invention, in the future, a substantially greater share of available raw materials in the form of wood chips will be used in a cost-effective way, entailing substantial cost savings, environmental improvement, as well as an increased utilization rate of existing raw wood materials. The method will benefit the environment, as well as many interest groups (e.g., forest owners and consumers), due to improvements, e.g., in the form of increased income and reduced costs, including optimized usage of energy from an environmental perspective.

BRIEF DESCRIPTION OF THE INVENTION

One object of the present invention is to provide a method or device that will create an effective solution to the aforementioned problems, which is achieved by a device or method according to the attached claims. A modern harvester with a mobile wood chipper according to the invention will be able to produce about the same amount of round wood (approx. 40 to 70 sq. m. of round wood per hour) as previously, involving marginal extra costs for the chip production itself, which in turn entails substantially lower chip production costs than with current methods. Using today's methods, hauling of forest waste, from logging to the processing yard, costs itself an estimated SEK 50 per sq. m., whereas hauling green chips according to the invention is assumed to cost less than SEK 15 per sq. m., involving total savings of above 50 percent, when handing is done according to the invention.

BRIEF DESCRIPTION OF THE DRAWING

The attached figure shows schematically a device in side elevation according to an embodiment of the invention.

DETAILED DESCRIPTION

FIG. 2 shows a platform belonging to a mobile unit, e.g., connected to a conventional single-grip harvester, or forming a conventional forwarder chassis. The complete unit 1 will cover a smaller area of the surface of a conventional platform 2 that is used for such machines.

Briefly described, unit 1 comprises a wood chipper 3, a conveyor 4, a compactor 5, and a packaging device 6. Wood chipper 3 has a loading device 30 for feeding raw wood material. A casing 40 included in a screw conveyor 4 with a screw 41 provided therein is arranged at an outfeed end 31 of wood chipper. A compactor device 5 is placed in connection with the end of screw 41. The compactor 5 device comprises a nozzle 50 shaped like a truncated cone. The angle of the cone is preferably in the 1 to 6° range, more preferably 2 to 5°, whereby the nozzle obtains a relatively great length (typically in the 200 to 500 mm range) in order to create the desired compaction. Compactor 5 is preferably also provided with a type of vibration device 51 for further chip compaction in the area of nozzle 50. A packaging device 6 is provided in connection with the converging end of the nozzle. Packaging device 6 comprises in part a casing part 60 through which compacted chips 9 are conveyed in order to be fed further into a tubular packaging device 7. This tubular packaging device 7 is journaled around tubular part 60. Packaging device 7 is gradually filled when chips 9 are fed out, thereby forming an elongated tubular sausage 8. A seal 80 is located at each end of a finished package 8. This seal 80 is advantageously installed by means of a sealing device 61 positioned in direct contact with the end of outfeed pipe 60.

Chips 9 are thus fed directly from wood chipper 3 and compressed in said compressor 5 by means of screw 41 before packaging, thus forming a continuous “sausage” 8, when fed into casing 7. The packaging is advantageously dimensioned 400 to 600 mm in diameter and 2500 to 3500 mm in length. The main purpose of compression is twofold: Making the sausage sufficiently stable for automatic handling and increasing its content: Package 8 may automatically be sealed at the ends 80 and separated from the rest of casing 7.

Chip compressor 5 and packaging device 6, hereafter referred to as “chipper 1,” are preferably designed to be used along with a conventional single-grip harvester equipped with a wood chipper 3. The single grip harvester is the most prevalent method used in machine logging, and works like this: The operator cuts a selected tree, then strips the branches from the trunk to be able to remove timber and pulpwood. When reaching the preset minimum diameter, the operator releases the top and moves on to the next tree. The method of wood chipper 1 differs, in that a new element is added, whereby the limit for round wood and chips becomes a new factor. The natural growth of a tree in a stand is characterized by the volume of the branch being inversely proportional to the diameter of the trunk, i.e., the bulk of the branch is situated at the top. Modern crosscutting systems make it possible to specify a new way of crosscutting thereby establishing a new break-even point for profitability. In the current price situation, the top diameter will henceforth likely be selected substantially wider than is the case today. When the length of the round part has been optimized, preferably by means of a crosscutting computer (not shown), the operator feeds the remaining part of the trunk directly into wood chipper 3. This processing part should not affect the capacity of the harvester to any great extent. Cut chips 9 should be made to drop directly into the infeed part of screw 41, which performs some of the compaction of chips 9 before these arrive at nozzle 50, which generally is responsible for handing the majority of compaction. After compaction, chips 9 are conveyed into a stocking 7 forming the moveable “chip sausage” 8. When reaching its desired length, sealing 80 and separation should be done. The filled chip sausage 8 is then placed on the ground, preferably such, which includes its shape or dimension, that the harvester is not prevented from being hauled.

The design consists of several elements that interact in a way that interferes minimally with the harvester. Below follows an explanation of the preferred aspects of the design. As for stem wood, chipper 3 should have a minimum diameter of 200 mm, and the infeed chute (not shown) should be configured for minimum operator intervention, i.e., a type of wide conical chute guiding the log toward the chipper infeed substantially regardless of how the log is placed in the chute. Preferably, a self-fed conical wood chipper 3 is used, which is a great advantage. The feed rate of wood chipper 3 may only under unusual circumstances be limiting for the capacity of the harvester, and should be at least 8 m/min, preferably 10 to 15 m/min. With the latter capacity, a wood chipper has an estimated power requirement of 110 to 130 kW. Wood chipper 3 is preferably powered by a variable transmission (not shown), which may be hydrostatic, hydrodynamic, or mechanical, however, hydrostatic operation is most preferable, due to the simplicity of rpm control. Wood chipper 3 and the infeed chute are advantageously placed on a kingpin 32 or another device allowing it to be turned, preferably a minimum of 180 degrees.

A screw conveyor 4 is placed in direct connection with outfeed 31 of the chipper and will in part compress the chips in a nozzle 50 or cone in order to further compress the chips. Screw conveyor 4 should preferably have a substantial diameter (450 to 600 mm). Screw 20 requires great torque and should therefore preferably be powered by a hydrostatic transmission (not shown) with ample mechanical gear reduction (preferably in the 41:51:20 range). Providing an option for controlling the rotational speed of screw 41 may entail a great operational advantage, as the chip supply varies with the type and diameter of the tree. Chip supply should preferably be stopped, when sausage 8 is being sealed, which in this type of design preferably requires an automatic sensor informing the operator to temporarily stop further infeed to wood chipper 3. The rotational speed of the screw should preferably be controlled by a computer with some type of limit sensor in order to detect when the desired length of sausage 8 has been reached, and then stopping the screw, in part coupled to the chipper power requirement (i.e., small P=low production=lower speed). The power requirement for chipper 3 is closely related to chip volume. Since the operator normally programs the harvester for tree type, this information may be used advantageously for programming chipper 3, as well.

Nozzle 50, i.e., the device that performs a part (often the main part) of the compaction should be equipped optimally with means 5 for vibrator support. The chip fractions obtained from chipper 3 have a great spread. It is desirable to cut chips into as large a fraction as possible, i.e., preferably 60 to 70 mm, as with shorter chips, the power requirement increases. Since chipping of stem wood, branches, and needles is done, fractions will naturally differ greatly, which is, however, often advantageous during compaction. In order to increase further the degree of compaction, means 51 may be installed for vibrator operation of the nozzle 50.

Packaging casing 7, i.e., the stocking that will enclose the finished sausage 8, should be of the ventilating type and sufficiently strong for the finished unit to be handled with ordinary forks. Due to this and in combination with compaction, the dimensional stability of the sausage becomes sufficiently great for transport on an ordinary forwarder. Chips 9 consisting of ordinary natural material will not impact the environment negatively in the event of an accident. The combination of the form of material, resin content, etc., the diameter of the sausage, and compaction results in a substantially stable unit that may be handled and transported by a plurality of currently existing equipment.

The sealing device 6 may be variously designed, whereby sealing of sausage 8 is done safely and quickly. Many different types of long known tying devices may be used, e.g., reapers and binders, whereby one preferred solution is to rotate sausage 8 one revolution, in principle like a peppermint stick, before sealing by means of two sealing devices 80.<0} Having completed this, sausage 8 is chopped off between the seals 80 (not shown). Chopping of sausage 8 should be done after its sealing, which can be done, e.g., with a chain saw. Since the material is sticky, the seals need not be tight, which will facilitate the procedure. After sealing, sausage 8 can be placed on the ground for transport at a later time. Handling the sausage, i.e., placing it on the ground, is probably best done using a harvester crane.

The invention is described below in reference to a forest harvester. The operator applies the harvester unit (not shown) on a selected tree, severs it, provides information to the computer about the type of tree, and processes the tree according to the product range preset by the computer. Here, a new product range for chips 9 is added. This product range requires new parameters in the harvester computer accounting for the optimal value of trunk content. This optimization should take into consideration that the volume share of branches increases with decreasing diameter. With normal logging, there is always a substantial difference between coarse and fine. Smaller trunks should preferably be cut into chips without previous separation of round wood. As for wood decayed due to putrefaction, the invention, a substantial efficiency can occur, since this type of wood may be processed immediately to chips. The harvester operator must ensure that wood that is too coarse is not fed into wood chipper 3, including tops that cannot be handled by wood chipper 3. Naturally and for various reasons, there will be some trunks that cannot be chipped, however, this does not represent a loss in relation to current methods, since these trunks may be processed into round wood.

To gain the acceptance by harvester operators, the following should apply:

-   -   1. The power requirement should make possible the removal of         branches and cutting without restriction, when compared with         standard machines, whereby the power requirement should be         increased, preferably by approx. 100 kW.     -   2. The crosscutting computer should be reprogrammed such that         the new product range is automatically stored.     -   3. Sealing and length determination should be “automatic.”     -   4. Feeding new raw wood material (e.g., tops) during the sealing         process should be possible.

If these four requirements are met, it will not be difficult for operators to accept the method, especially if operator preferences in terms of shape and size are given ample consideration. The outfeed table should preferably be equipped with a detection radar (not shown) in order to avoid collision damage. The feeding of raw wood material will likely require some training, but here it should be considered that tops always tend to cause handling problems.

Mobile chip handling unit 1 may be mounted on several different chassis, whereby the following may be mentioned: For thinning, a newly designed unit with a cutting assembly also able to handle chip sausages may advantageously be used. A similar unit will be equipped with a powerful motor of at least 150 kW for harvesting the entire product range as chips. A conventional single-grip harvester with increased engine capacity may also be used in order to produce chips at the same time as ordinary processing. However, optional equipment, such as a separate engine may also be used. Moreover, chipper 1 may also be mounted on a conventional forwarder chassis with sufficient engine capacity.

Chippers 3 may be of different types, but preferably a conical screw chipper is used. Drum chippers and disk chippers may also be used.

Conveyor screw 41, another compaction component, should have a large diameter to length ratio (preferably between 1-2), i.e., the diameter of the chip sausage will affect the diameter of the screw. The screw 41 drive should preferably be of the hydrostatic type and feeding rpm preferably vary with the amount of supplied chips, which depends on the power consumption in wood chippers 3 in combination with tree selection. The screw drive can, of course, be exclusively mechanical or hydrodynamic, but these options often complicate control.

Nozzle 50, i.e., the device ensuring compaction of the chips, is a unit that may be designed in several different ways. In normal situations, it is desirable to achieve at least 20%, preferably 20 to 40% compaction, and higher compaction, if achieved, is advantageous in most cases.

Chip sausage 8 or package 8 may be modified depending on the logging system; In Scandinavia, a diameter of between 500 and 800 mm and a length of between 2000 and 3000 mm is often preferred. Chip content may vary between 0.5 and 1.5 cu. m. In the current situation, a volume matching a diameter of 500 mm and a length of 3000 mm would be optimal. A bag with a diameter of 1200 mm and a height of about 1500 mm providing a volume of 1.6 cu. m. is of course also conceivable, but this would likely result in more expensive haulage and a more difficult sealing technology. In daily situations, the simplest and safest packaging should mean a cylindrical sausage with the above dimensions. The outfeed track should be substantially horizontal and, when of correct length, the sausage should be rotated by a gripping device 82 (preferably also connected to an interacting device assisting in bringing about the adjusted/desired length), thereby twisting package content 9 with stocking 7 is or moving it along the longitudinal axis, similar to the principle used in the production of striped candy. Seal 80 may be either a tying device or, e.g., a riveting device. Dual seals are made on either side of what is intended to be the cut-off site (not shown). Sausage 8 is then separated from casing 7, and lifted by the harvesting assembly and placed on the ground beside the haulage road. During the sealing process or hauling, the driver (operator) will not be able to feed new material into wood chipper 3, which means that the time for sealing and hauling, normally not to exceed 20 seconds, is a parameter that should be set to a minimum delay.

As is obvious from the above that several parameters may be varied/optimized, e.g., the chip content in the sausage (if the diameter is increased from 500 to 600 mm, the content increases by 50%) and the degree of compaction. In most cases, the weight should not exceed 500 kg in order not to complicate haulage from forest to road.

The invention is not limited by what is described above, but may be modified within the scope of the following claims. Moreover, it is obvious that the exemplified schematic figure provides only outlines within the scope of which, a person skilled in the art may devise many different kinds of concrete embodiments. 

1-10. (canceled)
 11. A device for mobile handling of wood chips comprising: a mobile platform on which is provided a wood chipper; a chip conveyor connected to the wood chipper; a compaction device; a packaging device; and a packaging casing arranged at the packaging device, provided in order to package chips in a tubular package by means of the said packaging casing during use, wherein said chip conveyor comprises a screw conveyor having a screw, the outfeed end of the screw conveyor is constructed to feed chips into the compaction device placed in connection with said packaging device during use.
 12. A device according to claim 11, wherein said compaction device comprises a nozzle.
 13. A device according to claim 12, wherein a vibration-excitation means is provided at the said nozzle.
 14. A device according to claim 11, wherein said compaction device comprises a sealing device.
 15. A device according to claim 11, wherein said mobile platform is provided on a harvester with a crosscutting computer comprising software that automatically suggests and/or determines the product range of the selected raw wood material to be produced, whereby chips are included in the product range.
 16. A method of mobile handling of wood chips comprising: a mobile platform on which is provided a wood chipper; a chip conveyor connected to the chipper, the conveyor comprising a screw; a compaction device; a packaging device; and a packaging casing provided at the packaging device provided to pack chips in a tubular package by means of said packaging casing, wherein the method comprises: feeding said chips from said wood chipper using the screw into the compaction device positioned in connection with said packaging device.
 17. A method according to claim 16, wherein chips in said compaction device are fed through a nozzle.
 18. A method according to claim 17, wherein chips are subjected to processing at the said nozzle by means of a vibration-excitation means.
 19. A method according to claim 16, further comprising sealing packaged chips using a sealing device.
 20. A method according to claim 16, wherein said mobile platform is provided at a harvester with a crosscutting computer comprising software that automatically suggests and/or determines the product range of the selected raw wood material to be produced, whereby chips are included in the said product range. 